Shear stress derived enhancement of LPSO deformation and DRX behavior for Mg-11Gd-4Y-2Zn-0.5Zr alloy

doi:10.1016/j.metadv.2026.04.006

Abstract

Abstract:

Mg-11Gd-4Y-2Zn-0.5Zr alloy with long-period stacking ordered (LPSO) phases exhibits excellent high-temperature strength and ductility. In this paper, the influence of compressive stress (hot compression) and shear stress (hot torsion) on the deformation of LPSO phases and dynamic recrystallization (DRX) behavior was investigated at 450 °C and 0.01 s⁻¹. Microstructural evolution was characterized using optical microscopy (OM), scanning electron microscopy (SEM), and electron backscattered diffraction (EBSD). The results revealed distinct stress-mode dependencies: DRX area fractions were notably higher under shear stress than under compressive stress. Moreover, the LPSO phases exhibited noticeably different deformation behaviors: intragranular lamellar LPSO phases exhibited weaker kinking deformation with lower kink angles during torsion, while intergranular block LPSO phases suffered more severe fragmentation under shear stress. Theoretical analysis confirmed that the enhanced fragmentation under torsion promotes DRX via particle-stimulated nucleation (PSN) mechanism. Analysis of in-grain misorientation axes (IGMA) and effective Schmid factors (ESF) demonstrated that more pyramidal <c+a>II slips were preferentially activated under shear stress. Such increased activation of pyramidal <c+a>II slip facilitates DRX nucleation by generating a higher density of low-angle grain boundaries and sub-grains compared to that under compressive stress.

Key words: Mg-Gd-Y-Zn-Zr alloy, Long-period stacking ordered (LPSO) phase, Torsion, Dynamic recrystallization, Particle-stimulated nucleation

Ce Zheng, Shuaifeng Chen, Ming Cheng, Shihong Zhang, Yingju Li, Yuansheng Yang. Shear stress derived enhancement of LPSO deformation and DRX behavior for Mg-11Gd-4Y-2Zn-0.5Zr alloy[J]. Metals Advances, 2026, 46: 86-101.

Figures/Tables 21

Fig. 1. Dimensions of samples and the microstructure observation areas for (a) hot compression and (b) hot torsion conditions.

Table 1. Taylor axes corresponding to slip systems in Mg and its alloy [25].

Slip mode	Slip type	Taylor axes	Number of slip system
{0001}<11−20>	Basal <a>	<1−100>	3
{10−10}<1−210>	Prismatic <a>	<0001>	3
{10−11}<1−210>	Pyramidal <a>	<10−1−2>	6
{10−11}<11−2−3>	Pyramidal Ⅰ <c+a>	<−25 41 −16 9>	12
{11−22}<11−2−3>	Pyramidal Ⅱ <c+a>	<−1100>	6

Fig. 2. Rotation axis distribution for different slip systems of Mg alloys [24].

Fig. 3. (a) Effective stress-strain curves and (b) work hardening rate of hot compression and torsion conditions.

Fig. 4. Microstructure evolution of GWZK114 alloy during hot compression conditions (a) ε = 0; (b) ε = 0.3; (c) ε = 0.45; (d) ε = 0.6; (e) ε = 0.75; (f) ε = 0.9 (CD presents compression direction; and RD means radial direction of the sample).

Fig. 5. Microstructure evolution of GWZK114 alloy during hot torsion (a) center (ε = 0); (b) R1 (ε = 0.3); (c) R1.5 (ε = 0.45); (d) R2.0 (ε = 0.6); (e) R2.5 (ε = 0.75); (f) R3.0 (ε = 0.9) (TD presents torsion direction; and RD means radial direction of the sample).

Fig. 6. Kink bands of LPSO phases under compression and torsion conditions with different levels of strain (a-d) compression and (e-h) torsion.

Fig. 7. Evolution of kink angles for lamellar-shaped LPSO phases with strain for compression and torsion samples.

Fig. 8. Distribution of block-shaped LPSO phases under compression and torsion conditions with different levels of strain (a-d) compression and (e-h) torsion.

Fig. 9. Average diameter of block-shaped LPSO phase under hot compression and torsion.

Fig. 10. EBSD results of IPF for (a) compression sample, (b) torsion sample, (c) grain size distribution, (d) aspect ratio distribution.

Fig. 11. Pole figures of compression and torsion samples.

Fig. 12. Angle between basal slip plane of kinked LPSO and load axis.

Fig. 13. Effective Schmid factor (ESF) of LPSO phases with different orientations under compressive and shear stress states. (a) Schematic diagram and (b) ESF of LPSO phases with different orientations under compressive stress; (c) schematic diagram and (d) ESF of LPSO phases with different orientations under shear stress.

Fig. 14. EBSD figures for compression and torsion samples at strain of 0.9; (a-c) the misorientation angle distribution around block-shaped LPSO phases under compression; (d-f) the misorientation angle distribution around block-shaped LPSO phases under torsion.

Fig. 15. Detail analysis of the select grains from compressed and torsion samples (a, c, e, g, i) compressed sample; (b, d, f, h, j) torsion sample.

Table 2. Orientation dependence of the GWZK114 alloy under compression and torsion conditions.

Grains	Angle with Y axial (0 90 0) (°)	IGMA	Slip system	KAM	DRX area fraction
Com.1	20.9	<0001>	Pris.	Parallel lines	27.3%
Tor.1	22.4	<0001>+<uvt0>	Pris.+bas.+pyr.Ⅱ	Sub-grain	20.0%
Com.2	39.1	Uniform	Pris.+bas.+pyr.Ⅱ	Cross line+sub-grain	44.8%
Tor.2	45.7	<0001>	Pris.	Parallel lines	39.4%
Com.3	60.5	<0001>	Pris.	Cross lines	9.5%
Tor.3	59.5	Uniform	Pris.+bas.+pyr.Ⅱ	Parallel lines	53.7%
Com.4	68.2	<0001>	Pris.	Cross lines	26.6%
Tor.4	56.6	<uvt0>	Bas.+pyr.Ⅱ+pyr.Ⅰ	Parallel lines	32.8%
Com.5	84.8	Uniform	Pris.+bas.+pyr.Ⅱ	Cross lines	20.0%
Tor.5	90.2	<0001>+<uvt0>	Pris.+bas.+pyr.Ⅱ	Cross lines	40.9%

Fig. 16. Effective Schmid factor poles figures of different slip systems under (a) compression; (b) torsion conditions.

Fig. 17. Regions based on effective Schmid factor distribution in Fig. 16 under compression and torsion conditions.

Table 3. Dominated slip systems in the different regions of the (0001) pole figure.

Stress condition	Region A	Region B	Region C
Compression	Pyramidal<c+a>Ⅱ Pyramidal<c+a>Ⅰ	Basal<a> Prismatic<a> Pyramidal<a>	Prismatic<a> Pyramidal<a> Pyramidal<c+a>Ⅱ
Torsion	Pyramidal<c+a>Ⅱ Pyramidal<c+a>Ⅰ	Basal<a> Prismatic<a> Pyramidal<a>	Basal<a> Prismatic<a> Pyramidal<a> Pyramidal<c+a>

Fig. 18. Schematic illustrations for DRX mechanism for (a) compression and (b) torsion samples.

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